Facebook Post: Message or Link

Joocial posts requests to Facebook as type 'Message'. In order to measure the number of shares of an article (K2 item), one can query 'total_count' of 'link_stat' in Facebook Graph. However since the post is a 'message' it cannot measure any interactions.
If the post on Facebook is of the type 'Link', measuring the 'total_count' is ok.
My question is: how can I post to Facebook as type 'link'? I tried filling in the 'URL' field in the request, however the post to Facebook is still as type 'Message'.
Thanks for helping me out.